Re: [RFC 3/3] tools/memory-model: Add litmus test for RMW + smp_mb__after_atomic()

From: Andrea Parri <parri.andrea@gmail.com>
To: Boqun Feng <boqun.feng@gmail.com>
Cc: linux-kernel@vger.kernel.org,
	Alan Stern <stern@rowland.harvard.edu>,
	Will Deacon <will@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Nicholas Piggin <npiggin@gmail.com>,
	David Howells <dhowells@redhat.com>,
	Jade Alglave <j.alglave@ucl.ac.uk>,
	Luc Maranget <luc.maranget@inria.fr>,
	"Paul E. McKenney" <paulmck@kernel.org>,
	Akira Yokosawa <akiyks@gmail.com>,
	Daniel Lustig <dlustig@nvidia.com>,
	Jonathan Corbet <corbet@lwn.net>,
	linux-arch@vger.kernel.org, linux-doc@vger.kernel.org
Subject: Re: [RFC 3/3] tools/memory-model: Add litmus test for RMW + smp_mb__after_atomic()
Date: Fri, 14 Feb 2020 09:18:26 +0100	[thread overview]
Message-ID: <20200214081826.GB17708@andrea> (raw)
In-Reply-To: <20200214061537.GA20408@debian-boqun.qqnc3lrjykvubdpftowmye0fmh.lx.internal.cloudapp.net>

> > @@ -0,0 +1,29 @@
> > +C Atomic-RMW+mb__after_atomic-is-strong-acquire
> > +
> > +(*
> > + * Result: Never
> > + *
> > + * Test of an atomic RMW followed by a smp_mb__after_atomic() is
> > + * "strong-acquire": both the read and write part of the RMW is ordered before
> > + * the subsequential memory accesses.
> > + *)
> > +
> > +{
> > +}
> > +
> > +P0(int *x, atomic_t *y)
> > +{
> > +	r0 = READ_ONCE(*x);
> > +	smp_rmb();
> > +	r1 = atomic_read(y);

IIRC, klitmus7 needs a declaration for these local variables, say
(trying to keep herd7 happy):

P0(int *x, atomic_t *y)
{
	int r0;
	int r1;

	r0 = READ_ONCE(*x);
	smp_rmb();
	r1 = atomic_read(y);
}

Thanks,
  Andrea